THE ELECTRIC RAILWAY. 745 



conservation of energy is afforded by the fact that a dynamo will not 

 only generate an electric current if it be revolved by mechanical means, 

 but that it will itself revolve, if an electric current be sent through it 

 from an exterior source ; so that it not only can transform mechanical 

 energy into electrical energy, but can also transform electrical into 

 mechanical energy. When used for this purpose it is called an " elec- 

 tro-motor," and sometimes an " electric engine." 



Not only, hoAvever, is it necessary for an engine to be capable of 

 doing a certain kind of work ; it is also necessary for it to be capable 

 of doing it economically, and it is for this reason that such a great 

 future is prophesied for electric engines. For, while an excellent and 

 elaborately constructed stationary steam-engine can produce but a 

 small fraction of the energy it absorbs, a good electric engine (or elec- 

 tro-motor) will return seventy-five per cent of the electric energy given 

 it by the generating dynamo. For the reason, however, that no eco- 

 nomical means of generating large currents are yet discovered, except 

 the method described of first burning coal, the use of electric machin- 

 ery is at present restricted to certain industries. Now, one of these 

 industries is believed to be railroading. 



The opinion is generally held that railroad companies desire to 

 obtain as large a return as possible upon their investment, and there- 

 fore to run their trains as cheaply as possible. If this be true, the 

 value of an electric railway will become obvious, when one remembers 

 that, of necessity, the present locomotive is wasteful in the extreme> 

 and that in an electric railway a large and economical stationary 

 engine renders its mechanical energy to a large and economical dynamo 

 which sends an electric current to an economical motor on an electric 

 locomotive. This motor is connected with the driving-wheels by 

 gearing, belting, or other suitable devices, so that its revolution pro- 

 duces a revolution of the driving-Avheels and a consequent progress- 

 ive motion of the electric locomotive, in the same way that the 

 engine of a steam-locomotive produces a rotary motion of the driv- 

 ing-wheels, and a consequent progressive motion of the steam-loco- 

 motive. There is a certain loss of electricity in passing from the 

 dynamo to the motor on the locomotive, both from leakage and from 

 overcoming the resistance of the conductors ; but, for distances not 

 too great, this loss, added to the losses in converting the mechanical 

 energy of the stationary engine into electrical energy, and in recon- 

 verting this electrical energy back into mechanical energy by the 

 motor, is not equal to the loss inseparable from even the best steam- 

 locomotives. 



It will be, of course, noticed that it is necessary constantly to 

 maintain an electrical connection between the electro-motor on the 

 locomotive and the stationary dynamo, in all positions of the locomo- 

 tive. To accomplish this effectively, a number of systems have been 

 invented. By one system the rails themselves act as conduciors, the 



